Compressed tablets (e.g., caplets) are known as one of the most cost effective, consumer friendly and convenient dosage forms available for delivering pharmaceutically active agents. Compressed tablets often involve multiple steps in order to incorporate pharmaceutically active agents into the form since only certain materials may be used for compression. The materials must have the correct compression characteristics such as flow and compressibility, in order to maintain operability on a tablet press, retain shape and form without breakage, and dissolve within an appropriate timeframe in the gastrointestinal tract. In order to achieve these characteristics, blends or powdered materials must often be granulated using high shear, chilsonation, or fluid bed techniques to increase the size and maintain a flowable particle shape. Methods for direct compression and wet granulation processes are known in the art, and are described in detail in, for example, Lachman, et al., The Theory and Practice of Industrial Pharmacy, Chapter 11 (3rd ed. 1986).
Compressed tablets have been used to deliver pharmaceutically active agents with a modified release profile. One means to make such tablets is to coat particles containing the pharmaceutically active agent with modified release polymers. However, these polymers often have the disadvantage of cracking under contact with the surrounding tablet matrix materials within the tablet upon compression. A cracked or ruptured coating may result in an pharmaceutically active agent, which no longer retains the intended modified release property. One means to overcome this issue was using a high level of plasticizers in the coating. However, plasticizers can also compromise the modified release properties of the polymer and/or lead to the portions of tablet sticking on the face of tablet tooling. When portions of the tablet stick, several issues may occur, including weight variation amongst individual tablets and removal of embossed markings. Another means to overcome these issues was the addition of high tensile strength polymers such as cellulose acetate to the coating. However, a disadvantage of this approach may include the use of solvents for applying the coating and/or the effect of the polymer in unfavorably changing the release properties of the coating.
The present invention provides for particles containing a pharmaceutically active agent that are coated with two film layers and that are compatible to be compressed in a tablet.